Certain "metallocenes" (especially bis-cyclopentadienyl complexes of group 4 metals) are highly productive catalysts for olefin polymerization when used in combination with an appropriate activator (see, for example, U.S. Pat. No. 4,542,199 (Sinn et al) and U.S. Pat. No. 5,198,401 (Hlatky and Turner).
Olefin polymerization catalysts having one cyclopentadienyl ligand and one phosphinimine ligand are disclosed in a commonly assigned patent application (Stephan et al).
We have now discovered a family of highly active olefin polymerization catalysts which do not contain a cyclopentadienyl ligand.